Field observations of wave‐driven circulation over spur and groove formations on a coral reef

Rogers, Justin S.; Monismith, Stephen G.; Dunbar, Robert B.; Koweek, David A.

doi:10.1002/2014jc010464

Cited by 26 publications

(37 citation statements)

References 37 publications

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“…There is an additional, albeit small, influence of the cross‐shore advective acceleration term. On the other hand, the alongshore tidal budget at 12mS suggests that advective acceleration is an equally important contributor to the momentum budget as the bottom drag, similar to what Rogers et al () found over a spur and groove formation on the fore‐reef. We hypothesize that the imbalance at the 12mS mooring is associated with a local acceleration of the flow.…”

Section: Discussionsupporting

confidence: 81%

An Alongshore Momentum Budget Over a Fringing Tropical Fore‐Reef

et al. 2018

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Existing momentum budgets over coral reefs have predominantly focused on cross‐reef dynamics, lacking analysis of alongshore processes. To complement existing cross‐reef research and enhance our understanding of forcing variability at the semidiurnal period, this study examines the σ–coordinate, depth‐averaged alongshore momentum budget over a fore‐reef as a function of tidal phase. The observations were gathered over a 3‐week timespan, between the 12‐ and 20‐m isobaths of a Hawaiian fringing reef system, focusing on two moorings on the 12‐m isobath, where median drag coefficients estimated from log fits are CD=0.0080[−0.002,+0.004] and CD=0.0023[−0.0006,+0.0009]. Analysis at one location shows that the unsteadiness, barotropic pressure gradient, and bottom drag are equally important, and their combination is sufficient to close the momentum budget. However, bottom drag is less important at the second mooring; the difference between unsteadiness and pressure gradient suggests that advective acceleration plays a significant role.

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Section: Discussionsupporting

confidence: 81%

An Alongshore Momentum Budget Over a Fringing Tropical Fore‐Reef

et al. 2018

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“…Physical measurements in a SaG system at Palmyra Atoll, a reef exposed to oceanic swell from the North Pacific, supported the modelling results, showing a persistent 1 cm s −1 offshore flow over the spurs and onshore flow over the grooves at depths of 8-11 m (Rogers et al, 2015). However, Rogers et al (2015) acknowledge that the model results for shallow zone have yet to be verified with field data as instruments were insufficiently shallow, further highlighting the difficulties of collecting data in the shallow, highly dynamic zone. In Grand Cayman Island, a reef exposed to the gentler waves of Caribbean, Roberts et al (1977) reported that currents in grooves seemed to be tidally dominated.…”

Section: Accepted M Manuscriptsupporting

confidence: 52%

“…(Palmyra Atoll; Rogers et al, 2015) and 4° (Molokai, Hawaii; Rogers et al, 2013). This highlights that gradient and width of the reef slope are determining factors in SaG formation.…”

Section: Accepted M Manuscriptmentioning

confidence: 88%

“…Applying this standardized classification elsewhere would help elucidate the complex processes driving SaG formation worldwide. Chevalier (1973);Grand Cayman: Roberts (1974); Palmyra: Rogers et al (2015); Bikini: Munk and Sargent (1954); Chagos: Sheppard (1981); Alphonse: Hamylton and Spencer (2011); Jamaica: Goreau (1959);Florida Keys: Shinn (1963);Mariana: Cloud (1959). The methodology by which these data were collected is described in supplementary Table S1.…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

“…SaG systems have been documented in every global reef province (e.g. Weydert, 1979;Sheppard, 1981;Shinn et al, 1981;Kan et al, 1997a;Rogers et al, 2015). They represent one of the most biodiverse and productive zones of modern reefs (Perry et al, 2013) and are believed to act as natural breakwaters (Munk and Sargent, 1954), regulating the hydrodynamic energy and nutrients received by reef platforms and thus affecting reef biogeography (Odum and Odum, 1955).…”

Section: Introductionmentioning

confidence: 99%

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A morphometric assessment and classification of coral reef spur and groove morphology

et al. 2016

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S0169-555X (16) This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.  Four classes of spurs and grooves are formally defined using remote sensing for global application. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPT Classes correspond to different formation mechanisms with implications for reef platform evolution. Waves are key drivers of feature morphology but width and slope of the fore reef are important. A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTConfidential manuscript submitted to Geomorphology AbstractSpurs and grooves (SaGs) are a common and important feature of coral reef fore slopes worldwide. However, they are difficult to access and hence their morphodynamics and formation are poorly understood. We use remote sensing, with extensive ground truthing, to measure SaG mophometrics and environmental factors at 11,430 grooves across 17 reefs in the southern Great Barrier Reef, Australia. We revealed strong positive correlations between groove length, orientation and wave exposure with longer, more closely-spaced grooves oriented easterly reflecting the dominant swell regime. Wave exposure was found to be the most important factor controlling SaG distribution and morphology. Gradient of the upper reef slope was also an important limiting factor, with SaGs less likely to develop in steeply sloping (>5°) areas. We used a subset of the morphometric data (11 reefs) to statistically define four classes of SaG. This classification scheme was tested on the remaining six reefs.SaGs in the four classes differ in morphology, groove substrate and coral cover. These differences provide insights into SaG formation mechanisms with implications to reef platform growth and evolution. We hypothesize SaG formation is dominated by coral growth processes at two classes and erosion processes at one class. A fourth class may represent relic features formed earlier in the Holocene transgression. The classes are comparable with SaGs elsewhere, suggesting the classification could be applied globally with the addition of new classes if necessary. While further research is required, we show remotely sensed SaG morphometrics can provide useful insights into reef platform evolution.

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Wave dynamics of a Pacific Atoll with high frictional effects

et al. 2016

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We report field measurements of waves and currents made from September 2011 to July 2014 on Palmyra Atoll in the central Pacific that were used in conjunction with the SWAN wave model to characterize the wave dynamics operant on the atoll. Our results indicate that wave energy is primarily from the north during the northern hemisphere winter and from the south in the northern hemisphere summer. Refraction of waves along the reef terraces due to variations in bathymetry leads to focusing of waves in specific locations. Bottom friction, modeled with a modified bottom roughness formulation, is the significant source of wave energy dissipation on the atoll, a result that is consistent with available observations of wave damping on Palmyra. Indeed modeled wave dissipation rates from bottom friction are on average larger than dissipation rates due to breaking and are an order of magnitude larger than what has been observed on other, less geometrically complex reefs, a result which should be corroborated with future in situ measurements. The SWAN wave model with a modified bottom friction formulation better predicts bulk wave energy properties than the existing formulation at our measurement stations. The near bed squared velocity, a proxy for bottom stress, shows strong spatial variability across the atoll and exerts control over geomorphic structure and benthic community composition.

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Field observations of wave‐driven circulation over spur and groove formations on a coral reef

Cited by 26 publications

References 37 publications

An Alongshore Momentum Budget Over a Fringing Tropical Fore‐Reef

An Alongshore Momentum Budget Over a Fringing Tropical Fore‐Reef

A morphometric assessment and classification of coral reef spur and groove morphology

Wave dynamics of a Pacific Atoll with high frictional effects

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